Unfortunately, fresh jalapeno slices are nowhere to be found in the actual sandwich. Instead, there is a spicy Mexican chili sauce that curiously looks creamy and not-very-spicy. In addition to the sauce, there's a thigh meat battered and fried chicken patty, onions, lettuce, and tomatoes. The bun seems interesting with a smattering of various grains atop (sesame, oats, flax seeds, and a few others it looks like).
Translated (go go Google Translate!) accounts from the Taiwan branch's Facebook page seem to indicate that the sandwich is just a little spicy.
All-in-all, it doesn't sound very Mexican at all.
The sandwich is offered for a special lunch/dinner price of $99 NT (~$3.40 US) and for $125 NT (~$4.29 US) at other times.
It looks like the final leg of the tour starts in December and will feature a taste of Europe.